Yes calcs are correct.
It depends on the rapid speed you need and what kernel you can set Mach to reliably. If you keep the kernel at 25KHz the max rapid will be 23Inch per min, if you go to 45KHz it would be 42IPM
45KHz is probably the best you can expect reliably, some computers can do better. If you need more than 42IPM then drop down to 1/4 step and that will give you 84IPM max.
Hood